1. Field of the Invention
The invention relates to an external vehicle mirror and, more particularly, to an external vehicle mirror having powered extension between laterally-retracted and laterally-extended positions. In one aspect, the invention relates to a slip clutch for the powered extension function that enables the mirror to be manually extended or retracted without damage to the motor or the transmission.
2. Description of the Related Art
External mirror systems are ubiquitous for contemporary vehicles and have long been used to aid the driver in operating the vehicle, especially in improving the rearward view of the driver. Over time, more and more functionality has been incorporated into the mirror system. For example, it is common to extend the reflective element assembly of the mirror system away from the vehicle, which is useful when towing a trailer. Mirror systems incorporating both a powered fold and powered extension functionality are well-known. Examples of such mirror systems are disclosed in U.S. Pat. Nos. 6,276,808 and 6,213,609, assigned to the assignee of the current application, and are incorporated herein by reference.
In one embodiment of the powered extension function, the reflective element of assembly is extended away from the vehicle by the motor-driven rotation of an elongated drive screw which causes a threaded nut driver to travel longitudinally along the drive screw. The nut driver is connected to a movable frame piece to which is attached the reflective element, which translates relative to the drive screw with the movement of the nut driver. Depending upon the direction of rotation of the drive screw, the reflective element is either extended away from the vehicle or retracted toward the vehicle.
At times it may be desirable to manually translate the reflective element assembly between the extended and retracted positions. For example, after leaving the vehicle, the owner may wish to retract the reflective element assembly without having to reenter and restart the vehicle to do so. Similarly, it may be desirable to accommodate inadvertent forcing of the reflective element assembly into the retracted or extended positions with minimal damage to the motor, transmission, drive shaft, or other mirror system components. A conventional powerextend assembly having a tightly interlocking configuration of components (including the interlocking of motor gears or a drive screw) will generally be unable to accommodate such manual translation without damage to the components, particularly the motor and drive screw.